The present invention relates to a horizontal bidirectional deflection system image display which is suitable for display of a highly precise image.
In recent years, digital techniques have been developed, and particularly the costs of large-capacity memories are reduced. The applications of image processing techniques using the memories have significantly progressed. In JP-A-8-172543, a bidirectional deflection system CRT (Cathode-Ray Tube) display has been proposed in order to reduce the power consumption at a high horizontal scanning frequency.
When the bidirectional deflection system CRT display which has been proposed in the prior art is put on the market as an actual image display such as a monitor apparatus for display or a television receiver, the function of graphically displaying set contents, channels, and the like by OSD (On Screen Display) is required.
FIG. 13(a) is a diagram showing an example of display of a video signal and an OSD graphic signal in conventional forward scanning, FIG. 13(b) is a diagram showing a phase relationship among a horizontal synchronizing signal, a video signal, a graphic signal (character signal), and a display switching control signal at the time of the forward scanning.
In FIG. 13(a), an ellipse on each of forward scanning lines L1, L2, and L3 indicates an on-screen display by the graphic signal. In FIG. 13(b), the video signal is outputted when the display switching control signal is at a low level, while the graphic signal is outputted when the display switching control signal is at a high level. Display by the video signal as well as on-screen display by the graphic signal are thus performed in each of forward scanning periods.
However, a technique for performing on-screen display in the bidirectional deflection system image display has not been established.
On the other hand, in the television receiver, a technique for enhancing the contour of an image using a method of horizontal speed modulation to improve focusing characteristics of a CRT has been widely employed. In JP-A-6-284309, the application of a speed modulation technique to a bidirectional deflection system has been proposed.
In the bidirectional deflection system image display, however, on-screen display and horizontal speed modulation are difficult to perform.
Therefore, it is desired to establish a technique making on-screen display possible in the bidirectional deflection system image display as well as to further establish a technique for performing horizontal speed modulation in the bidirectional deflection system image display capable of performing such on-screen display.
An object of the present invention is to provide a bidirectional deflection system image display capable of performing on-screen display.
Another object of the present invention is to provide a bidirectional deflection system image display capable of performing on-screen display and horizontal speed modulation.
Still another object of the present invention is to provide a horizontal speed modulator (horizontal velocity modulator) used for a bidirectional deflection system image display capable of performing on-screen display.
An image display according to an aspect of the present invention is an image display for displaying an image by forward scanning and backward scanning, comprising inverting means for inverting on the time axis a video signal and a graphic signal which correspond to the backward scanning; switching and outputting means for switching and outputting the video signal and the graphic signal which correspond to the forward scanning and switching and outputting the video signal and the graphic signal, which have been inverted, corresponding to the backward scanning; and display means for displaying the video signal and the graphic signal which have been outputted by the forward scanning and the backward scanning.
Therefore, the video signal and the graphic signal can be displayed by the forward scanning and the backward scanning. Consequently, a bidirectional deflection system image display capable of performing on-screen display is realized.
An image display according to another aspect of the present invention is an image display for displaying an image by forward scanning and backward scanning, comprising video signal inverting means for alternately inverting the output order of an inputted video signal between the forward scanning and the backward scanning; graphic signal generating means for generating a graphic signal; graphic signal inverting means for alternately inverting the output order of the graphic signal generated by the graphic signal generating means between the forward scanning and the backward scanning; display signal switching means for switching the display of the video signal outputted from the video signal inverting means and the graphic signal outputted from the graphic signal inverting means; switching and inverting means for alternately inverting the order of switching by the display signal switching means between the forward scanning and the backward scanning; and display means for displaying the video signal and the graphic signal which are outputted from the display signal switching means by the forward scanning and the backward scanning.
In the image display, the output order of the inputted video signal is alternately inverted between the forward scanning and the backward scanning, and the output order of the graphic signal is alternately inverted between the forward scanning and the backward scanning. The display of the video signal and the graphic signal is switched. In this case, the order of switching is alternately inverted between the forward scanning and the backward scanning. Therefore, the video signal and the graphic signal are displayed by the forward scanning and the backward scanning.
Consequently, a bidirectional deflection system image display capable of performing on-screen display is realized.
An image display according to still another aspect of the present invention is an image display for displaying an image by forward scanning and backward scanning, comprising synthesizing means for synthesizing a video signal and a graphic signal which correspond to the forward scanning and the backward scanning; inverting means for inverting on the time axis the video signal and the graphic signal, which have been synthesized, corresponding to the backward scanning; and display means for displaying by the forward scanning the video signal and the graphic signal, which have been synthesized, corresponding to the forward scanning, and displaying by the backward scanning the video signal and the graphic signal, which have been inverted, corresponding to the backward scanning.
Therefore, the video signal and the graphic signal can be displayed by the forward scannig and the backward scanning. Consequently, a bidirectional deflection system image display capable of performing on-screen display is realized.
An image display according to still another aspect of the present invention is an image display for displaying an image by forward scanning and backward scanning, comprising graphic signal generating means for generating a graphic signal; synthesizing means for synthesizing an inputted video signal and the graphic signal outputted from the graphic signal generating means; video signal inverting means for alternately inverting the output order of the video signal and the graphic signal which have been synthesized by the synthesizing means between the forward scanning and the backward scanning; and display means for displaying the video signal and the graphic signal which are outputted from the video signal inverting means by the forward scanning and the backward scanning.
In the image display, the video signal and the graphic signal which are inputted are synthesized. The output order of the video signal and the graphic signal which have been synthesized is alternately inverted between the forward scanning and the backward scanning.
Therefore, the video signal and the graphic signal are displayed by the forward scanning and the backward scanning. Consequently, a bidirectional deflection system image display capable of performing on-screen display is realized.
An image display according to still another aspect of the present invention is an image display for displaying an image by forward scanning and backward scanning, comprising inverting means for inverting on the time axis a video signal corresponding to the backward scanning; switching and outputting means for switching and outputting the video signal and the graphic signal which correspond to the forward scanning; masking means for masking a portion, corresponding to a displayed portion of the graphic signal in the upper or lower forward scanning, in the video signal corresponding to the backward scanning; and display means for displaying by the forward scanning the video signal and the graphic signal which correspond to the forward scanning, and displaying by the backward scanning the video signal, which has been partially masked, corresponding to the backward scanning.
Therefore, the video signal and the graphic signal are displayed by the forward scanning, and the video signal whose portion corresponding to the displayed portion of the graphic signal has been masked is displayed by the backward scanning. Consequently, a bidirectional deflection system image display capable of performing on-screen display only by the forward scanning is realized.
An image display according to still another aspect of the present invention is an image display for displaying an image by forward scanning and backward scanning, comprising video signal inverting means for alternately inverting the output order of an inputted video signal by the forward scanning and the backward scanning; graphic signal generating means for generating a graphic signal; display signal switching means for switching the display of the video signal outputted from the video signal inverting means and the graphic signal outputted from the graphic signal generating means as well as masking a portion, corresponding to a displayed portion of the graphic signal in the upper or lower forward scanning, in the video signal corresponding to the backward scanning with a mask signal generated by the graphic signal generating means; switching and inverting means for alternately inverting the order of switching by the display signal switching means between the forward scanning and the backward scanning; and display means for displaying by the forward scanning the video signal and the graphic signal which are outputted from the display signal switching means, and displaying by the backward scanning the video signal and the mask signal which are outputted from the display signal switching means.
In the image display, the output order of the inputted video signal is alternately inverted between the forward scanning and the backward scanning. Further, the display of the video signal and the graphic signal is switched, and the portion, corresponding to the displayed portion of the graphic signal in the upper or lower forward scanning, in the video signal corresponding to the backward scanning is masked with the mask signal. In this case, the order of switching is alternately inverted between the forward scanning and the backward scanning.
Therefore, the video signal and tie graphic signal are displayed by the forward scanning, and the video signal which has been partially masked is displayed by the backward scanning. Consequently, a bidirectional deflection system image display capable of performing on-screen display only by the forward scanning is realized.
An image display according to still another aspect of the present invention is an image display for displaying an image by forward scanning and backward scanning, comprising synthesizing means for synthesizing a video signal and a graphic signal which correspond to the forward scanning and the backward scanning; masking means for masking a portion, corresponding to a displayed portion of the graphic signal in the upper or lower forward scanning, in the video signal corresponding to the backward scanning; inverting means for inverting on the time axis the video signal, which has been partially masked, corresponding to the backward scanning; and display means for displaying by the forward scanning the video signal and the graphic signal which correspond to the forward scanning, and displaying by the backward scanning the video signal, which has been partially masked, corresponding to the backward scanning.
Therefore, the video signal and the graphic signal are displayed by the forward scanning, and the video signal whose portion corresponding to the displayed portion of the graphic signal has been masked is displayed by the backward scanning. Consequently, a bidirectional deflection system image display capable of performing on-screen display only by the forward scanning is realized.
An image display according to still another aspect of the present invention is an image display for displaying an image by forward scanning and backward scanning, comprising graphic signal generating means for generating a graphic signal; synthesizing means for synthesizing an inputted video signal and the graphic signal outputted from the graphic signal generating means; masking means receiving the video signal and the graphic signal which have been synthesized by the synthesizing means, and masking a portion, corresponding to a displayed portion of the graphic signal in the upper or lower forward scanning, in the video signal corresponding to the backward scanning and outputting the video signal and the graphic signal; video signal inverting means for alternately inverting the output order of the video signal and the graphic signal which are outputted from the masking means between the forward scanning and the backward scanning; and display means for displaying by the forward scanning the video signal and the graphic signal, corresponding to the forward scanning, which are outputted from the video signal inverting means, and displaying by the backward scanning the video signal, which has been partially masked, outputted from the video signal inverting means.
In the image display, the video signal and the graphic signal which are inputted are synthesized. Further, the portion, corresponding to the displayed portion of the graphic signal in the upper or lower forward scanning, in the video signal corresponding to the backward scanning is masked, to output the video signal and the graphic signal. The output order of the video signal and the graphic signal is alternately inverted between the forward scanning and the backward scanning.
Therefore, the video signal and the graphic signal are displayed by the forward scanning, and the video signal which has been partially masked is displayed by the backward scanning. Consequently, a bidirectional deflection system image display capable of performing on-screen display only by the forward scanning is realized.
An image display according to still another aspect of the present invention is an image display for displaying an image by forward scanning and backward scanning, comprising inverting means for alternately inverting the output order of a video signal and a graphic signal between the forward scanning and the backward scanning while synthesizing the video signal and the graphic signal; display means for displaying the video signal and the graphic signal which have been outputted by the forward scanning and the backward scanning; generating means for generating a horizontal speed modulating signal (horizontal velocity modulating signal) by differentiating the video signal and the graphic signal which have been outputted; and horizontal speed modulating means (horizontal velocity modulating means) for performing horizontal speed modulation (horizontal velocity modulation) on the basis of the generated horizontal speed modulating signal.
In the image display, the video signal and the graphic signal are displayed by the forward scanning and the backward scanning, and the video signal and the graphic signal are differentiated so that the horizontal speed modulating signal is generated. The horizontal speed modulation is performed on the basis of the generated horizontal speed modulation.
Consequently, a bidirectional deflection system image display capable of performing on-screen display and horizontal speed modulation is realized.
The image display may further comprise level control means for controlling a portion, corresponding to the graphic signal, in the horizontal speed modulating signal generated by the generating means at a predetermined level.
In this case, the portion, corresponding to the graphic signal, in the horizontal speed modulating signal, is controlled, thereby making it possible to prevent the image quality of a character portion which is on-screen displayed from being degraded.
An image display according to still another aspect of the present invention is an image display for displaying an image by forward scanning and backward scanning, comprising synthesizing and inverting means for alternately inverting the output order of the video signal and the graphic signal which are inputted between the forward scanning and the backward scanning while synthesizing the video signal and the graphic signal; display means for displaying the video signal and the graphic signal which are outputted from the synthesizing and inverting means by the forward scanning and the backward scanning; horizontal speed modulating signal generating means for differentiating the video signal and the graphic signal which are outputted from the synthesizing and inverting means to generate the horizontal signal modulating signal; and horizontal speed modulating means for performing horizontal speed modulation on the basis of the horizontal speed modulating signal outputted from a horizontal speed modulating signal generating means.
In the image display, the output order of the video signal and the graphic signal which are inputted is alternately inverted between the forward scanning and the backward scanning while the video signal and the graphic signal are being synthesized. The video signal and the graphic signal which have been synthesized are displayed by the forward scanning and the backward scanning. The video signal and the graphic signal which have been synthesized are differentiated so that the horizontal speed modulating signal is generated. The horizontal speed modulation is performed on the basis of the horizontal speed modulating signal.
Consequently, a bidirectional deflection system image display capable of performing on-screen display and horizontal speed modulation is realized.
The horizontal speed modulating signal generating means may comprise differentiating means for differentiating the video signal and the graphic signal which are outputted from the synthesizing and inverting means, and polarity inverting means for alternately inverting the polarity of an output signal of the differentiating means between the forward scanning and the backward scanning.
The image display may further comprise horizontal speed modulating signal control means for controlling a portion, corresponding to the graphic signal, in the horizontal speed modulating signal generated by the horizontal speed modulating signal generating means.
In this case, the portion, corresponding to the graphic signal, in the horizontal speed modulating signal is controlled, thereby making it possible to prevent the image quality of a character portion which is on-screen displayed from being degraded.
The horizontal speed modulating signal control means may set the portion, corresponding to the graphic signal, in the horizontal speed modulating signal generated by the horizontal speed modulating signal generating means at a predetermined level.
In this case, the portion, corresponding to the graphic signal, in the horizontal speed modulating signal is set at a predetermined level. Consequently, the contour of the character portion is not enhanced. As a result, the balance of the character portion which is on-screen displayed is maintained.
The synthesizing and inverting means may comprise first synthesizing means for switching and outputting the video signal and the graphic signal on the basis of a switching signal having a pulse corresponding to the position where the graphic signal is displayed, to synthesize the video signal and the graphic signal, and video signal inverting means for alternately inverting the output order of the video signal and the graphic signal which have been synthesized by the first synthesizing means between the forward scanning and the backward scanning. The horizontal speed modulating signal control means may comprise switching signal inverting means for alternately inverting the switching signal on the time axis between the forward scanning and the backward scanning, and control means for controlling a portion, corresponding to the graphic signal, in the horizontal speed modulating signal generated by the horizontal speed modulating signal generating means on the basis of the switching signal which has been inverted by the switching signal inverting means.
In this case, the video signal and the graphic signal are switched and outputted on the basis of the switching signal having the pulse corresponding to the position where the graphic signal is displayed, so that the video signal and the graphic signal are synthesized. The output order of the video signal and the graphic signal which have been synthesized is alternately inverted between the forward scanning and the backward scanning. The, switching signal is alternately inverted on the time axis between the forward scanning and the backward scanning. Further, the portion, corresponding to the graphic signal, in the horizontal speed modulating signal is controlled on the basis of the inverted switching signal.
The horizontal speed modulating signal control means may further comprise pulse width expanding means for expanding the width of the pulse of the switching signal which has been inverted by the switching signal inverting means.
In this case, the width of the pulse of the switching signal is expanded, thereby making it possible to reliably control the portion, corresponding to the graphic signal, in the horizontal speed modulating signal.
The pulse width expanding means may control the amount of expansion of the width of the pulse of the switching signal depending on the frequency band of the horizontal speed modulating signal generated by the horizontal speed modulating signal generating means.
In this case, the amount of expansion of the width of the pulse of the switching signal is controlled depending on the frequency band of the horizontal speed modulating signal. Accordingly, the portion, corresponding to the graphic signal, in the horizontal speed modulating signal can be reliably controlled depending on the frequency band of the horizontal speed modulating signal.
The image display may further comprise binarizing means for binarizing the switching signal and feeding the binarized switching signal to the switching signal inverting means.
In this case, the switching signal is binarized. On the basis of the binarized switching signal, the display of the video signal and the graphic signal is switched, and the horizontal speed modulating signal is controlled.
The video signal inverting means may comprise first storing means for inputting and storing the video signal and the graphic signal, corresponding to the forward scanning, which have been outputted from the first synthesizing means as well as outputting the video signal and the graphic signal which have been stored in the same order as that at the time of the input, second storing means for inputting in a predetermined order and storing the video signal and the graphic signal, corresponding to the backward scanning, which have been outputted from the first synthesizing means as well as outputting the video signal and the graphic signal which have been stored in an order reverse to that at the time of the input, and second synthesizing means for synthesizing the video signal and the graphic signal which are outputted from the first storing means and the video signal and the graphic signal which are outputted from the second storing means. The switching signal inverting means may comprise third storing means for inputting in a predetermined order and storing the switching signal corresponding to the forward scanning as well as outputting the stored switching signal in the same order as that at the time of the input, fourth storing means for inputting in a predetermined order and storing the switching signal corresponding to the backward scanning as well as outputting the stored switching signal in an order reverse to that at the time of the input, and third synthesizing means for synthesizing the switching signal outputted from the third storing means and the switching signal outputted from the fourth storing means.
In this case, the video signal and the graphic signal, corresponding to the forward scanning, which have been synthesized are inputted to the first storing means in a predetermined order and stored therein, and the video signal and the graphic signal which have been stored in the first storing means are outputted in the same order as that at the time of the input. Further, the video signal and the graphic signal, corresponding to the forward scanning, which have been synthesized are inputted to the second storing means in a predetermined order and stored therein, and the video signal and the graphic signal which have been stored in the second storing means are outputted in an order reverse to that at the time of the input. The video signal and the graphic signal which are outputted from the first storing means and the video signal and the graphic signal which are outputted from the second storing means are synthesized. The output order of the video signal and the graphic signal is thus alternately inverted between the forward scanning and the backward scanning.
On the other hand, the switching signal corresponding to the forward scanning is inputted to the third storing means in a predetermined order and stored therein, and the switching signal which has been stored in the third storing means is outputted in the same order as that at the time of the input. Further, the switching signal corresponding to the backward scanning is inputted to the fourth storing means in a predetermined order and stored therein, and the switching signal which has been stored in the fourth storing means is outputted in an order reverse to that at the time of the input. The switching signal outputted from the third storing means and the switching signal outputted from the fourth storing means are synthesized. The switching signal is thus alternately inverted on the time axis between the forward scanning and the backward scanning.
The image display may further comprise format converting means for converting the format of the inputted graphic signal into the format of the inputted video signal.
In this case, the format of the inputted graphic signal is converted into the format of the inputted video signal, so that the signals are synthesized.
A horizontal speed modulator (horizontal velocity modulator) according to still another aspect of the present invention is a horizontal speed modulator used for an image display for displaying an image by forward scanning and backward scanning, comprising synthesizing and inverting means for alternately inverting the output order of a video signal and a graphic signal which are inputted between the forward scanning and the backward scanning while synthesizing the video signal and the graphic signal; horizontal speed modulating signal generating means for differentiating the video signal and the graphic signal which are outputted from the synthesizing and inverting meals, to generate a horizontal speed modulating signal; horizontal speed modulating means for performing horizontal speed modulation on the basis of the horizontal speed modulating signal outputted from the horizontal speed modulating signal generating means; and horizontal speed modulating signal control means for controlling a portion, corresponding to the graphic signal, in the horizontal speed modulating signal generated by the horizontal speed modulating signal generating means.
In the horizontal speed modulator, the output order of the video signal and the graphic signal which are inputted is alternately inverted between the forward scanning and the backward scanning while the video signal and the graphic signal are being synthesized. The video signal and the graphic signal which have been synthesized are differentiated so that the horizontal speed modulating signal is generated. The horizontal speed modulation is performed on the basis of the horizontal speed modulating signal.
In this case, the portion, corresponding to the graphic signal, in the horizontal speed modulating signal is controlled, thereby making it possible to prevent the image quality of the character portion which is on-screen displayed from being degraded.
The horizontal speed modulating signal generating means may comprise differentiating means for differentiating the video signal and the graphic signal which are outputted from the synthesizing and inverting means, and polarity inverting means for alternately inverting the polarity of an output signal of the differentiating means between the forward scanning and the backward scanning.
The horizontal speed modulating signal control means may set the portion, corresponding to the graphic signal, in the horizontal speed modulating signal generated by the horizontal speed modulating signal generating means at a predetermined level.
In this case, the portion, corresponding to the graphic signal, in the horizontal speed modulating signal is set at a predetermined level. Consequently, the contour of the character portion is not enhanced. As a result, the balance of the character portion which is on-screen displayed is maintained.
The synthesizing and inverting means may comprise synthesizing means for switching and outputting the video signal and the graphic signal on the basis of a switching signal having a pulse corresponding to the position where the graphic signal is displayed, to synthesize the video signal and the graphic signal, and video signal inverting means for alternately inverting the output order of the video signal and the graphic signal which have been synthesized by the synthesizing means between the forward scanning and the backward scanning. The horizontal speed modulating signal control means may comprise switching signal inverting means for alternately inverting the switching signal on the time axis between the forward scanning and the backward scanning, and control means for controlling a portion, corresponding to the graphic signal, in the horizontal speed modulating signal generated by the horizontal speed modulating signal generating means on the basis of the switching signal which has been inverted by the switching signal inverting means.
In this case, the video signal and the graphic signal are switched and outputted on the basis of the switching signal having the pulse corresponding to the position where the graphic signal is displayed, so that the video signal and the graphic signal are synthesized. The output order of the video signal and the graphic signal which have been synthesized is alternately inverted between the forward scanning and the backward scanning. The switching signal is alternately inverted on the time axis between the forward scanning and the backward scanning. Further, the portion, corresponding to the graphic signal, in the horizontal speed modulating signal is controlled on the basis of the inverted switching signal.
The horizontal speed modulating signal control means may further comprise pulse width expanding means for expanding the width of the pulse of the switching signal which has been inverted by the switching signal inverting means.
In this case, the width of the pulse of the switching signal is expanded, thereby making it possible to reliably control the portion, corresponding to the graphic signal, in the horizontal speed modulating signal.
As described in the foregoing, according to the present invention, a bidirectional deflection system image display capable of performing on-screen display is realized. Further, there is provided a bidirectional deflection system image display capable of performing on-screen display and horizontal speed modulation. Particularly, the portion, corresponding to the graphic signal, in the horizontal speed modulating signal is controlled, thereby making it possible to prevent the image quality of the character portion which is on-screen displayed from being degraded.